重载的可加减乘的点（向量）模板

#include<cstdio>
#include<cmath>
#include<iostream>
#include<cstring>
#include<string>
#include<vector>
#include<algorithm>
typedef long long ll;
using namespace std;
class point{
public:
    int x,y;
    point(){
        x = 0,y = 0;
    }
    point(int xx,int yy){
        x = xx;y = yy;
    }
    double mod(){//向量的膜
        return sqrt(x*x+y*y);
    }
    friend istream& operator >> (istream &,point &);
    friend ostream& operator << (ostream &,point );

    point operator + (point A);
    point operator - (point A);
    ll operator * (point A);
    bool operator == (point A);
};
istream & operator >> (istream &input,point &A){
    input >> A.x >> A.y;
    return input;
}
ostream & operator << (ostream &output,point A){
    output << A.x << " " << A.y;
    return output;
}
point point::operator + (point A){
    point C;
    C.x = x + A.x;C.y = y + A.y;
    return C;
}
point point::operator - (point A){
    point C;
    C.x = x - A.x;C.y = y - A.y;
    return C;
}
ll point::operator * (point A){
    return x*A.x + y*A.y;
}
bool point::operator == (point A){
    if(x == A.x && y == A.y)
        return true;
    return false;
}
int main(void){
    point x,y,z;
    cin >> x;
    cout << x.mod() << endl;


    return 0;
}